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I'm a great believer in making your unit tests as easy to read and understand as possible. I was thinking about how I could improve my tests the other day and thought about using extension methods to create a more fluent way of creating complex assertions.

Which I hope you'll agree reads a lot easier than those three assumptions on separate lines. Also, note that I have added the ability to use a predicate for when there isn't a method which quite matches your needs.

After seeing Jeffrey Palermo's SmartBag (part 1 and part 2) I was inspired to create my own version which was more specific to my needs. For one I'm a lover of the IEnumerable<T> interface, especially when combined with the power of LINQ for Objects.

Anyway, enough of my waffle, here's the code for the class.

﻿using System;

using System.Collections.Generic;

using System.Collections;

using System.Text;

namespace SmartBag

{

public class SmartBag

{

private Hashtable _hashtable;

publicSmartBag()

{

this._hashtable =newHashtable();

}

publicvoid Add<T>(T item)

{

List<T> list;

if(!this._hashtable.ContainsKey(typeof(T)))

this._hashtable.Add(typeof(T),new List<T>());

list =this._hashtable[typeof(T)] as List<T>;

list.Add(item);

}

public IEnumerable<T> Get<T>()

{

if(!this._hashtable.ContainsKey(typeof(T)))

throw newIndexOutOfRangeException(string.Format("There are no entries for {0}",typeof(T).Name));

foreach(T item in this._hashtable[typeof(T)] as List<T>)

yield return item;

}

}

}

There are basically two methods to it, Add and Get. Add adds items of the specified type to a list of that type. Get retrieves the list of the specified type.

Below are my test cases which should give you some ideas of how you can use it.

foreach(Object item in bag.Get<Object>()) { }// must enumerate for it to be evaluated

}

[Test]

publicvoidShouldBeAbleToAddChildAsADifferentType()

{

SmartBag bag =newSmartBag();

bag.Add(newParent());

bag.Add(newChild());

Assert.AreEqual(1, bag.Get<Parent>().Count());

Assert.AreEqual(1, bag.Get<Child>().Count());

}

private class Parent : IContract

{

}

private class Child : Parent

{

}

private interface IContract

{

}

}

}

To begin with this is a basic idea. I hope to utilise it in an upcoming project and it will probably look a bit different after I've used it in anger. Something I can see I might need is to extract an interface to make testing easier but I've left that out for now as YAGNI may apply.